Electrical control



1942- J. L. BONANNO I 2,291,944

ELECTRICAL CNTROL Filed March 4, 1941 lN VE NTO R JOSEPH L. BON/INNO fBY L MM ATTORNEY Patented Aug. 4, 1942 J STAL ELECTRICAL CONTROLApplication March 4, 1941, Serial No. 381,&59

4 Claims.

The present invention relates to electrical controls, and is moreparticularly directed toward the provision of shafts with shaft turningknobs made of molded material.

Many forms of electrical apparatus employ re- Volvably mounted shaftsfor effecting operation of some part and this shaft is actuated by anaccessible knob, this being preferably made of molded material toprovide the desired contour, appearance and design and in some instancesto provide insulation about the end of the shaft.

The present invention contemplates an improved form of knob and shaftdesigned for inexpensive manufacture and ease of assembly anddisassembly.

According to the present invention the shaft is provided with splines tomake it non-circular and the knob is provided with a hub having a boreto fit the shaft and slits to fit the` splines and the hub is providedwith a spring acting to insure that the knob fits the hub very tightlywhen in place.

The accompanying drawing shows, for purposes of illustrating the presentinvention, one of the many embodiments in which the invention may takeform, it being understood that the drawing is illustrative of theinvention rather than limiting the same.

In the drawing:

Figures 1 and 2 are side elevational views of a control shaft;

Figures 3 and 4 are Views illustrating the knob in place on the shaft,portions of the knob being shown in section; and

Figure 5 is a view similar to Figure 3 showing the knob alone.

A shaft o shown in Figures 1 and 2 has a configuration suitable forholding a switch contact, and is provided with an upper cylindricalportion ll and two splines indicated at !2, l2. The upper ends of thesesplines are bevelled as indicated at 13, and preferably slope downwardlyand outwardly as will be apparent in Figure 2. The upper end of theshaft is bevelled as indicated at !4.

The knob !5 is made of molded insulating material. It has a hub portion!6 with a central bore Il of such diameter as to receive the body of theshaft H. It has two slots IB, l8 which extend from the bottom of the hub16 up nearly to the top of the knob.

As shown in the drawing the hub has an upper portion !9 of slightlylarger diameter than the lower portion, and this portion receives aspring 20 tensioned to squeeze the hub inwardly. This spring is pressedon to the insulating material after it has been molded and acts tonarrow the slot lil as will be apparent from Figur-e 5. The knob can bereadily pressed onto the shaft by bringing the slots in alignment withthe splines and, owing to the bevelled surfaces provided, the splinesmay readily enter the slots and spread the hub against the tension ofthe spring. With this arrangement the knob can be made inexpensively andplaced on the shaft easily and in a manner that insures its remaining inposition until such time as it is necessary to remove it. The removal ofthe knob is not difficult and does not impair its structure orefiiciency.

As shown in the drawing the knob has a skirt portion 2| of suitableornamental shape, 'and this skirt portion covers the spring and the hub.While the drawing shows the spring 20 as having a gap opposite one ofthe slots in thehub of the knob this is of no importance for the springcan be forced into a position without regard to its angular positionabout the hub.

It is obvious that the invention may be embodied in many forms andconstructions within the scope of the claims and I wish it to beunderstood that the particular form shown is but one of the many forms.Various modifications and changes being possible, I do not otherwiselimit myself in any way with respect thereto.

What is claimed is:

1. In combination, a splined metal shaft, a molded insulating knobhaving a hub provided with a bore to fit the shaft and longitudinalslots to fit the splines, and a contractile spring embracing the hub andtending to close the slots.

2. In combination, a metal shaft having splines whose ends are spacedfrom the end of the shaft, an insulating knob of molded material havinga hub provided with a bore to fit the body of the shaft, andlongitudinal slots to fit the splines, and a hub embracing spring whichsqueezes the slots laterally to facilitate grip-ping the splines and theshaft.

3. In combination, a knob made of molded insulating material and havinga hub provided with a cylindrical bore and two longitudinally extendingslots extending through the walls of the bore, a spring substantiallyencircling the hub and tending to close the slots and constrict thedimension of the bore, and a splined shaft onto which the knob may bepressed, the spring yielding to allow the slots to open up to receivethe splines and squeezing the parts into frictional engagement.

4. The combination such as claimed in claim 3, wherein the end of theshaft and the ends of the plnes are bevelled to acilitate spreading theJ OSEPH L. BONANNO.

